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On radiative corrections to inverse beta decay at low energies

Oleksandr Tomalak

TL;DR

This work delivers a precision calculation of electromagnetic radiative corrections to inverse beta decay at reactor antineutrino energies by employing heavy-baryon chiral perturbation theory to coherently blend QED, electroweak, and QCD effects. The authors provide a fully analytic phase-space treatment of bremsstrahlung beyond the static limit and supply the first positron energy spectrum for radiative IBD, using low-energy constants such as $g_V(\mu_\chi=m_e)=1.02499(13)$, $\lambda=g_A/g_V=1.2754(13)$, and $V_{ud}=0.97348(31)$ within the $\overline{\mathrm{MS}}_{\chi}$ scheme. The results yield a total cross section accuracy at the permille level and a total relative uncertainty around $1.85\permil$ across reactor energies, with dominant uncertainties from $\lambda$ and $V_{ud}$, and show modest ($\sim 1-2\%$) shifts relative to previous parameterizations. These improvements enhance reactor antineutrino flux normalization, precision oscillation measurements, and searches for new physics, while providing detailed spectra and distributions for detector simulations and potential applications to supernova neutrino interactions.

Abstract

We compute electromagnetic radiative corrections in the inverse beta decay, $\barν_e + p \rightarrow e^+ + n$, at reactor antineutrino energies within the heavy baryon chiral perturbation theory, provide the most accurate cross-section predictions for this process, and present a complete error budget. For the first time, we consistently include quantum electrodynamics, chromodynamics, and electroweak contributions and present the positron energy spectrum accounting for radiative corrections. Our calculation also improves on previous evaluations by incorporating permille-level contributions. The results can be readily applied to normalize the reactor antineutrino flux, make precise measurements of neutrino oscillation parameters, and search for new physics at nuclear power plants.

On radiative corrections to inverse beta decay at low energies

TL;DR

This work delivers a precision calculation of electromagnetic radiative corrections to inverse beta decay at reactor antineutrino energies by employing heavy-baryon chiral perturbation theory to coherently blend QED, electroweak, and QCD effects. The authors provide a fully analytic phase-space treatment of bremsstrahlung beyond the static limit and supply the first positron energy spectrum for radiative IBD, using low-energy constants such as , , and within the scheme. The results yield a total cross section accuracy at the permille level and a total relative uncertainty around across reactor energies, with dominant uncertainties from and , and show modest () shifts relative to previous parameterizations. These improvements enhance reactor antineutrino flux normalization, precision oscillation measurements, and searches for new physics, while providing detailed spectra and distributions for detector simulations and potential applications to supernova neutrino interactions.

Abstract

We compute electromagnetic radiative corrections in the inverse beta decay, , at reactor antineutrino energies within the heavy baryon chiral perturbation theory, provide the most accurate cross-section predictions for this process, and present a complete error budget. For the first time, we consistently include quantum electrodynamics, chromodynamics, and electroweak contributions and present the positron energy spectrum accounting for radiative corrections. Our calculation also improves on previous evaluations by incorporating permille-level contributions. The results can be readily applied to normalize the reactor antineutrino flux, make precise measurements of neutrino oscillation parameters, and search for new physics at nuclear power plants.

Paper Structure

This paper contains 6 sections, 1 equation, 4 figures.

Table of Contents

  1. Introduction
  2. Inverse beta decay
  3. QED radiative corrections
  4. Results and discussion
  5. Conclusion
  6. Acknowledgments

Figures (4)

  • Figure 1: One-loop virtual QED correction in IBD.
  • Figure 2: Leading in nucleon recoil one-photon bremsstrahlung contributions to IBD process: $\overline{\nu}_e + p \rightarrow e^+ + n + \gamma$.
  • Figure 3: Total IBD cross section is presented as a function of the antineutrino energy $E_{\overline{\nu}_e}$ in the upper panel. The relative uncertainty, dominated by experimental errors of $\lambda$ and $V_{ud}$, is shown in the lower panel. Our result is compared to the cross-section parameterization in Ref. Strumia:2003zx, labeled as "Strumia 2003", predictions based on the treatment of radiative corrections in Ref. Kurylov:2002vj, labeled as "Kurylov 2002", and radiative corrections from Refs. Fayans:1985uejVogel:1999zyFukugita:2004cqRaha:2011aa, labeled as "Raha 2011".
  • Figure 4: Relative contribution of QED radiative corrections to the positron and electromagnetic energy spectra in IBD is presented for the typical antineutrino energy $E_{\overline{\nu}_e}= 3.5~\mathrm{MeV}$ as a function of the positron or electromagnetic energy. We compare our calculation to the electromagnetic energy spectrum in Refs. Fayans:1985uejVogel:1999zyFukugita:2004cqRaha:2011aa, labeled as "static limit". The left panel illustrates the radiative kinematic region, while the right panel represents the narrow range of the elastic IBD. $\overline{E}$ refers either to the positron or electromagnetic energy in the right panel.